2.4.2 String literal concatenation

Multiple adjacent string literals (delimited by whitespace), possibly
using different quoting conventions, are allowed, and their meaning is
the same as their concatenation. Thus, "hello" 'world' is
equivalent to "helloworld". This feature can be used to reduce
the number of backslashes needed, to split long strings conveniently
across long lines, or even to add comments to parts of strings, for
example:

Note that this feature is defined at the syntactical level, but
implemented at compile time. The `+' operator must be used to
concatenate string expressions at run time. Also note that literal
concatenation can use different quoting styles for each component
(even mixing raw strings and triple quoted strings).